Electrophotographic copying apparatus

ABSTRACT

A copying apparatus for producing a visible image of an original on a copy sheet which has a conductive base and a dielectric surface. The original is supported by support means. An electrostatic latent image of the original is formed on a photoconductive surface of a photoconductive plate by charging means and an optical assembly. The copy sheet is fed by sheet feed means in such a way that the dielectric surface of the copy sheet faces and is against the photoconductive surface on which the electrostatic latent image is formed. The electrostatic latent image is transferred from the photoconductive surface to the dielectric surface of the copy sheet by charge transfer means. The electrostatic latent image transferred onto the dielectric surface of the copy sheet is converted to a visible image by developing means.

United States Patent [1 1 Yamaguchi et al.

[ 1 Nov. 5, 1974 ELECTROPHOTOGRAPHIC COPYING APPARATUS [73] Assignee: Matsushita Electriclndustrial Co.,

Ltd., Kadoma, Japan [22 Filed: Sept. 24, 1971 [21] Appl. No.: 183,479

[30] Foreign Application Priority Data UNITED STATES PATENTS 2/1970 Robinson et al 3/1970 Uhlenberg 5/1970 Cirimele et al. 355/16 12/1971 Sage 355/ll Primary ExaminerRobert P. Greiner Attorney, Agent, or Firm-Wenderoth, Lind & Ponack [57] ABSTRACT A copying apparatus for producing a visible image of an original on a copy sheet which has a conductive base and a dielectric surface. The original is supported by support means. An electrostatic latent image of the original is formed on a photoconductive surface of a photoconductive plate by charging means and an optical assembly. The copy sheet is fed by sheet feed means in such a way that the dielectric surface of the copy sheet faces and is against the photoconductive surface on which the electrostatic latent image is formed. The electrostatic latent image is transferred from the photoconductive surface to the dielectric surface of the copy sheet by charge transfer means. The electrostatic latent image transferred onto the dielectric surface of the copy sheet is converted to a visible image by developing means 9 Claims, 6 Drawing Figures 101 I lei PMENTEUNDV 5:914 38461019 sum 2 IF 4 INVENTORS S O YAMAG H1 ASH! KATA 1A wmw/fzm ATTORNEYS PATENTEDRUV 5 m4 3; 846; 01 9 sum 3 or a 1N VENTORS ISAO YAMAGUCHI 63 F IG- 5 HlTASHI KATAYAMA ATTORNEYS PAIENTEDRBV SW4 3.8461019 SIEEI MJF 4 INVENTORS ISAO YAMAGUCHI HITASHI KATAYAMA Wdfld l udk ATTORNEYS FIELD OF THE INVENTION This invention relates to a copying apparatus, and more paticularly to a new and improved photoelectrostatic reproducing apparatus using a process of transferring a latent electrostatic image from a photoconductive plate to dielectric material.

BACKGROUND OF THE INVENTION In the conventional electrophotographic apparatus, a visible image is formed on a surface of a photoconductive plate by the known technique. For example, the surface of the photoconductive plate is electrostatically charged and an image of an original is optically projected onto a charged surface so that a charge pattern of the desired original is produced on said surface. The charge pattern is then converted into a visible image by applying the developing material onto the surface of the photoconductive plate. A copy sheet is superposed on the surface of a photoconductive plate on which the visible image is formed previously, and is separated from the surface so that the formed visible image is transferred from the surface of the photoconductive plate to the copy sheet. After the visible image is transferred to the copy sheet, a small quantity of the developing material still remains on the surface of the photoconductive plate. This small quantity of developing material deteriorates the image the next time an image is reproduced from the photoconductive plate. Therefore, a cleaning device is necessary for scraping the remained developing material from the photoconductive surface before the next reproduction process starts. Such a cleaning device usually has a complex construction and occupies a great deal of space inside the copying apparatus.

The conventional electrophotographic copying apparatus using a powder transfer method employs the socalled slit exposure method in which a partial image of a desired original is continuously projected onto a moving photoconductive plate. The advantages of the slit exposure method are the smaller amount of power required for the illumination of the original, uniform exposure and a high-copying speed. However, in the slit exposure method, it is necessary to move the photoconductive plate relatively to the original and perfectly synchronized relative movement is required between the photoconductive plate and the original in order to get a copy of excellent sharpness or with high resolution. This perfectly synchronized movement requires a mechanism which has a complex construction and works precisely so that the initial cost of the copying apparatus becomes high. In addition, troublesome maintainance is necessary.

The copying apparatus of this invention uses aiprocess of transferring an electrostatic latent image from a photoconductive surface to a dielectric surface of a copy sheet instead of transferring the visible image from the photoconductive surface to the copy sheet as in the conventional electrostatic copying apparatus. The electrostatic latent image transferred onto the dielectric surface of the copy sheet is developed by a conventional developing device in order to make it visible.

2 In other words, the electrostatic latent image is not developed on the photoconductive surface but is developed on the dielectric surface of the copy sheet. Therefore, the copying apparatus according to this invention does not require a complex and spaceoccupying cleaning device such as described above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new and improved photoelectrostatic copying apparatus.

Another obejct of this invention is to provide an improved copying apparatus employing a process of transferring an electrostatic latent image from a photoconductive surface to a copy sheet.

Another object of this invention is to provide an improved copying apparatus which does not have complex and space-occupying cleaning means for cleaning a photoconductive member.

Another object of this invention is to provide an improved copying apparatus having a new and simple mechanism for carrying out the slit exposure.

Another object of this invention is to provide a photoelectrostatic copying apparatus which has a compact and economically fabricated construction.

Another object of this invention is to provide a copying apparatus which can copy not only sheet material but also material from bound volumes, such as a page of a book.

Another object of this invention is to provide an improved copying apparatus employing a plane type photoconductive plate.

Another object of this invention is to provide a copying apparatus including new and improved means for feeding a single copy sheet during every copying cycle of the apparatus.

The other object of this invention is to provide a copying apparatus which is based on a charge transfer principle and which has an electrically conductive rubber member to press a copy sheet against a photoconductive plate having a latent image thereon.

In accordance with these and many other objects, an embodiment of the invention comprises a housing, a photoconductive plate having a conductive backing plate and a photoconductive surface, support means for supporting an original to be copied, charging means for imposing a uniform electrostatic charge on the photoconductive surface, an optical assembly for forming an electrostatic latent image of said original on said photoconductive surface, sheet feed means for feeding to the photoconducitve plate copy sheets each of which has a conductive base and a dielectric surface, one by one from sheet source so that the dielectric surface of said copy sheet faces and is against said photoconductive surface after the electrostatic latent image is formed on said photoconductive surface, charge transfer means for transferring said electrostatic latent image of said original from said photoconductive surface to said dielectric surface of said copy sheet, guide means for guiding said copy sheet in a predetermined path after said copy sheet is separated from said photoconductive surface, and developing means for converting said electrostatic latent image transferred onto said dielectric surface of said copy sheet to a visible image.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a copying apparatus according to the present invention.

FIG. 2 is an enlarged sectional view of a sheet feed means included in the copying apparatus.

FIG. 3 is an enlarged sectional view of the sheet feed means shown in FIG. 2 with the parts in different positions during the sheet feed operation.

FIG. 4 is an enlarged sectional view of a charge transfer means included in the copying apparatus.

FIG. 5 is an enlarged sectional view of the charge transfer means shown in FIG. 4 with the parts in position for the transfer operation.

FIG. 6 -is a schematic diagram of a circuit for controlling the operation of the copying apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 of the of the drawings illustrates a copying apparatus which embodies the present invention.

.The apparatus includes a housing 11. A mounting table indicated generally at 12 is provided on an upper 'portion of the housing 11, and is movably supported by of a single sheet, but also an original in a bound volume such as a certain page of a book, at the surface of the glass plate 15. The surface of the glass plate 15 is called the mounting surface.

A photoconductive plate 22 comprises a conductive backing plate 23, such as an aluminum plate, coated with a photoconductive layer 24. The photoconductive layer 24 used in this invention is a compound photoconductive layer which comprises amorphus selenium coated with organic photoconductor such as poly-N- Vinylcarbazole. Such a compound photoconductive layer is quite effective for a latent electrostatic image transfer process because a sufficient electrostatic charge can be applied to the photoconductive layer by means of corona charging means, and the image charge, which remains on the photoconductive layer after charge transfer, is completely discharged by being exposed to a discharge lamp. Therefore, the photoconductive plate can be used repeatedly for the charging, exposing, charge transferring, and discharging process. The surface of the photoconductive layer 24 is called the photoconductive surface.

The photoconductive plate 22 is secured to the mounting table 12, by the connecting member 21 so as to travel in the right and left direction together with said mounting table 12. The photoconductive layer 24 is located on the lower face of the photoconductive plate 22. The surface of the glass plate 15 is parallel to the surface of the photoconductive layer 24, and is also parallel to the travelling direction of the mounting table 12. Hereinafter, means which comprises the mounting table 12 and photoconductive plate 22 is designated the first means 27. The first means 27 is moved in the right and left direction by drive means comprising a reversible electric. motor 25, a drive chain 26, which drives driven sprocket 31 on drives shaft 32, and an endless chain 30 disposed between the driven sprocket 31 idler sprocket 31a on the idler shaft 32a. A part of the chain 30 is connected to the lower edges of the frame 14 so that the travel of the chain 30 moves the mounting table 12 and the photoconductive plate 22 in the right and left direction along the guide members 13, according to whether the rotational direction of the chain 30 is in a counterclockwise or in a clockwise direction.

The reversible motor 25 is controlled by control means, such as a control circuit 34, shown in FIG. 6. The motor 25 has two different speeds depending on the rotational direction. The rotating speed in a clockwise direction is greater than that in a counterclockwise direction. Therefore, the first means 27 travels slowly to the left in the F IG., that is, in a first direction. During the travel in the first direction, a uniform electrostatic charge is imposed on the surface of the photoconductive layer 24 and subsequently an image of the original is projected onto the surface of the photoconductive layer 24 so as to form an electrostatic latent image of the original on the surface. After the travel in the first direction is completed, the first means 27 quickly returns to the right, that is, in a second direction. During the travel in the second direction, the latent image is transferred from the photoconductive layer 24 to a dielectric layer of a copy sheet and any remaining image charge on the photoconductive layer 24 is discharged.

An optical assembly which is fixed to the housing 11 of the apparatus comprises illumination means 35, a lens unit 36, and mirrors 40 and 41. The optical assembly scans the original 20 to be reproduced and projects a flowing image of said original 20 on the photoconductive plate 22 in accordance with the relative movement between the first means 27 and the optical assembly. The illumination means 35 which includes a lamp 42 and a reflector 43 is positioned adjacent to an illumination slit 44 to illuminate the lower surface of the glass plate 15. The illumination slit 44 extends in a direction transverse to the direction of movement of the mounting table 12. The mirror 40 is mounted on a supporting member 45 which is secured to the housing 11, and is inclined at a 45 angle relative to the surface of the glass plate 15. The mirror 41 is mounted on a supporting member 46 which is secured to the housing 11, and is inclined at a angle relative to the mirror 40. The lens unit 36 includes a plurality of lens elements carried in a lens barrel 50 which is secured to the housing 11. The optical axis of the lens unit 36 is parallel to the direction of movement of the mounting table 12. The mirror- 40 receives light rays reflected from the original 20 through the illumination slit 44 and reflects them in a direction parallel to the direction of movement of the mounting table 12 and of the photoconductive plate 22. The mirror 41 reflects the light rays from the mirror 40 through the lens unit 36 at an angle of 90 upwardly and projects them through an exposure slit 51 onto the photoconductive plate 22.

The exposure slit 51 extends to the direction transverse to the travelling direction of the photoconductive plate 22. The lens unit 36 is adapted to transmit the reflected light from the original 20 and focus upon the surface of the photoconductive layer 24, and provides a 1:1 ratio between the size of the original 20 and the image projected onto the surface of the photoconductive layer 24. The projected image on the surface of the photoconductive layer 24 is an mirror image of the original 20. The combination of the optical assembly and the first means 27 produces a perfect synchronized relative movement between the original and the photoconductive plate 22.

Charging means 52 includes a corona discharge wire 53 which is stretched across the photoconductive plate 22 in a direction traverse to the travelling direction of the photoconductive plate 22. Said wire 53 is disposed parallel to the surface of the photoconductive plate 22 and spaced apart with a short distance from the photoconductive plate 22. The wire 53 is connected to a D.C. high voltage source capable of supplying several thousand volts potential, for example, 7,000 volts. The wire 53 is supported at the ends on a pair of spaced insulating blocks (not shown) mounted on the housing 11. A ground conductive shield 54 is mounted behind the wire 53 in order to improve the characteristic of the corona charge. The charging means 52 just described above is used for charging the photoconductive plate 22 before the photoconductive plate 22 is exposed to a light image at the exposure slit 51.

The copy sheets used in the copying apparatus according to this invention are dielectric material coated paper. Each copy sheet comprises a conductive base and a dielectric material coated on the base. Charge transfer means acts to transfer the latent electrostatic image from the surface of the photoconductive plate 22 to the dielectric surface of a copy sheet. First a copy sheet is positioned with the dielectric surface of the sheet facing the photoconductive plate which has had an electrostatic latent image thereon by the process above mentioned. The copy sheet is pressed by a conductive rubber roller 60 (which will be describedhereinafter) against the surface dielectric of the photoconductive plate 22 and the conductive base of the copy sheet is electrically coupled to theconductive backing plate 23 of the photoconductive plate 22 through the conductive rubber roller 60. Thereafter, the copy sheet is separated from the photoconductive plate 22 so that a latent electrostatic image corresponding to the original is transferred to the dielectric surface of the copy sheet.

Charge transfer means (FIG. 4) employed in the present invention, includes a conductive rubber roller 60 carried upon pivoted levers 6! which are normally biased by resilient means 62 so that the conductive roller 60 is retracted to a lower position spaced from the photoconductive plate 22. The other ends of levers 61 are connected to a plunger 64 of a solenoid 63. The conductive roller 60 is electrically connected to a ground potential to which the conductive backing plate 23 is electrically connected.

A pick-off means 65 (FIG. 3) is mounted on the photoconductive plate 22. It comprises pick-off levers 70 which are pivotally mounted on a shaft 71, and are normally biased by resilient means 72 to a position where the edges 73 of the pick-off levers 70 extend downward through openings 74 in the photoconductive plate 22. The force biasing the edge 73 of the pick-off lever 70 is not sufficient to overcome the resilient force provided by the resilient means 62 on the conductive roller 60.

It has been discovered, according to the present invention, that by using said electrically conductive rubber roller there can be reproduced a visible image having a more uniform image quality throughout the resultant copy sheet than could heretofore be produced. Said conductive rubber roller can be prepared by dispersing finely divided conductive particles such as graphite, metal oxide or metal powder in rubber. It is necessary that the electrical resistivity and hardness of the conductive rubber roller be controlled for the best result. A preferred electrical resistivity is less than IO ohms cm, and a preferred hardness is 30 to 60 Hs scale (JIS C type).

In the transfer operation (FIG. 5), the solenoid 63 is energized to retract the plunger 64 which is linked to the levers 61. The retraction of the plunger 64 pivots the levers 61 against the biasing of the resiliant means 62 to move and press the conductive rubber roller 60 against the photoconductive plate 22. After the conductive rubber roller 60 is pressed against the photoconductive plate 22, the copy sheet 79 is introduced between the roller 60 and the photoconductive plate 22 under the guidance of guide members 66 by sheet feed means which will be described hereinafter. The copy sheet 79 is brought into contact with the latent electrostatic image on the photoconductive plate 22 by the conductive roller 60, and is separated from the photoconductive plate 22 by a pick-off means 65. As previously mentioned, both the conductive rubber roller 60 and the conductive backing plate 23 are connected to a ground potential so that the latent electrostatic image is effectively transferred from the surface of the photoconductive layer 24 to the dielectric surface of the sheet 79.

Then, the leading edge of the copy sheet 79 after it is brought into contact with the photoconductive plate 22 by means of the resilient bias of the conductive roller 62, and as a result of the progress of the photoconductive plate 22 to the right, is picked off along the conductive roller 62 from the photoconductive plate 22 by means of the resiliently biased pick-off lever as shown in FIG. 5. The copy sheet 79 is transmitted to the next station under the guidance of guide means 75. The copy sheet is further transported by a pair of rollers 67 and a pair of guide members 68 to developing means. I

A suitable lamp 76 (FIG. 1) which works as a discharging means is positioned adjacent the charging means 52 to discharge any image charge remaining on the photoconductive layer 24 after the charge transfer process. The lamp 76 illuminates the photoconductive layer 24 during the time photoconductive plate 22 is moving to the right (FIG. I), that is, in a second direction.

The sheet feed means (FIG. 2) is operable to successively feed a single copy sheet 79 from the sheet source 83 during each copying cycle of the apparatus. A plurality of copy sheets are stacked on a sheet supporting table 80, with the layer of dielectric material thereof facing upwardly. Two separator arms 81 are fixed at the end portion of the sheet supporting table 80, and include two vertically extending portions 82, each of which provides a front stop for the stack of copy sheets 79 and two separator portions 84, each of which is bent from said portions 82 at a position adjacent to a corner of the top sheet.

The sheet feeding means includes new and improved means for controlling the movement of sheet engaging means into intermittent engagement of the top sheet 79 in the stack. Referring to FIG. 2 and FIG. 3, the sheet feeding means includes a pair of friction wheels 85, two levers 90 which have said wheels 85 rotatably mounted on one end thereof, and a pair of rollers 95 which are rotatably supported on the other ends of said levers 90. Said friction wheels 85 are fixedly mounted in spaced apart positions on a shaft 86 which is rotatably mounted between two levers 90. The two levers 90 are pivotally mounted on a fixed shaft 91 and are biased in the counterclockwise direction by springs 96. The shaft 91 has a driven pulley 92 rotably mounted thereon. Said driven pulley 92 is coupled by a flexible belt 93 to a pulley 94 rigidly secured to the shaft 86. The pulley 94 rotates the shaft 86 and the friction wheels 85 in a counter-clockwise direction about the axis of the shaft 86 to feed the sheets 79 to the right (FIG. 2). The driven pulley 92 is driven by a motor 121 (FIG. 1) in a counterclockwise direction by an appropriate transmitting mechanism (not shown). The two levers 90 are normally pivoted in a clockwise direction about the shaft 91 to a first position where the friction wheels 85 are out of engagement with the copy sheet 79 in the sheet source 83 as shown in FIG. 2, because the rollers 95 are pushed down by the lower surface of the photoconductive plate 22. As shown in FIG. 3, when the photoconductive plate 22 passes beyond the rollers 95 to the left, the levers 90 are pivoted in a counterclockwise direction about the shaft 86 by springs 96, so that the friction wheels 85 engage with the top sheet 79 in the sheet source 83. The top sheet 79 is then fed to the right by the friction wheels 85 and the leading edge of the top sheet 79 buckles slightly to permit the sheet 79 to pass beyond the separator arms 81. The sheet 79 is fed to the position between the photoconductive plate 22 and the conductive roller 60.

The developing means (FIG. 1) includes developing vessel 100, two pairs of rollers 101 and 102 at opposite ends of vessel 100, and guide members 103 located in the developing vessel 100. The rollers 101 and 102 are driven by the motor 121 by transmission means (not shown); The liquid developer within the feed tank 104 is fed through a small pipe 105 into the developing vessel 100 by gravity. When the leading edge of the copy sheet 79 is fed past the rollers 101 into an entrance opening 106 of the passageway defined by the guide members 103, this copy sheet is fed beneath the surface of the liquid developer and passes through the passageway. The leading edge of the copy sheet 79 leaves the developing passageway defined by the guide members 103 through an outlet opening 107 and is fed into the nip between the pair of continuously driven rollers 102. Then, the developed copy sheet is sent to drying means.

The drying means includes a pair of rollers 110, a heater 112, a fan 113, and guide members 114. The rollers 110 are driven by the motor 121 by transmission means (not shown). During the copy time the sheet is passing through the passageway defined by the guide members 114, the copy sheet is dried and the developed image on the copy sheet is fixed by the warm air from the fan 113 through the heater 112. The copy sheet with the developed image thereon is discharged through an outlet opening 115.

A control circuit is shown in FIG. 6 coordinates and controls the operation of the various components of the copying apparatus as will be described hereinafter. The apparatus is placed in condition for operation by placing a stack of copy sheets onto the sheet supporting table (FIG. 1). The apparatus is then prepared for operation by closing a main switch (FIG. 6) to supply conventional alternating current potential to the control circuit 34. This potential is applied to the winding of the motor 121 so that the friction wheels 85, rollers 101, 102 and 110 are rotated. This input potential is also applied to the fan 113 and the heater 112, so that a flow of warm air is produced. When a copy is to be made of an original 20 such as a page from the book, the page to be copied is placed on the glass plate 15 (FIG. 1). When an operator closes a start switch 112 (FIG. 6) in order to initiate the operation of the apparatus, a winding 123 of a relay 124 is energized and contacts 125, 126 and 130 are maintained in a closed condition. The closure of the contacts 130 connects the alternating current input potential to a DC. high voltage source 131 so that the corona discharge wire 53 is supplied with DC. potential. Thus the charging means 52 (FIG. 1) is placed in operation to apply a uniform electrostatic charge to the photoconductive layer as it passes over the charging means 52. Further, the closure of the contacts 130 (FIG. 6) energizes the lamp 42 so that the portion of the original 20 above the illumination slit 44 (FIG, 1) is illuminated. The light selectively reflected according to the original 20 is transmitted by the optical assembly so as to selectively discharge the uniformly charged surface of the photoconductive layer 24 at the exposure slit 51 (FIG. 1) and forms a latent electrostatic image corresponding to the original 20 to be copied.

The contacts 126 (FIG. 6) energize the reversible motor 25 to start the movement of the first means 27 in the left direction. During the movement of the mounting table 12 and photoconductive plate 22, a latent electrostatic image corresponding to the original 20 is continuously formed on the photoconductive layer 24. When the edge 97 of the photoconductive plate 22 passes over the rollers 95 (FIG. 3), the top sheet 79 is fed by the friction wheel 85 and the leading edge of the top sheet 79 buckles slightly to permit the sheet 79 to pass beyond the separator arms 81. The leading edge of the sheet 79 fed from from the sheet source 83 is guided between the guide members 66. When the leading edge of the sheet 79 is fed to the position between the photoconductive plate 22 and the conductive roller 60, the connecting member 21 of the mounting table 12 reaches a travel limiting switch 132 fixed to the housing 11 as shown in FIG. 1 and actuates the operation arm of the switch 132.

Upon the closure of the switch 132, the winding 134 of a relay 135 is energized (FIG. 6). Contacts 136, 141, and 142 of the relay 135 are maintained in a closed condition. A contact of the relay 135 is opened so that the winding 123 of the relay 124 is deenergized and the contacts 125, 126, and 130 are opened. The closure of the contact 141 energizes, the reversible motor 25 to cause it to rotate in a clockwise direction (FIG. 1) so that the motor 25 moves the mounting table 12 and the photoconductive plate 22 in the right direction. The closure of the contact 142 energizes the solenoid 63 (FIG. 5) to retract the plunger 64. The retraction of the plunger 64 causes the lever means 61 to pivot in a clockwise direction (FIG. 5) so that the conductive roller 60 is brought into engagement with the photoconductive plate 22. During the progress of the photoconductive plate 22 in the right direction, the

copy sheet 79 is pressed against the latent electrostatic image on the photoconductive plate 22 by the conductive roller 60, and is picked off from the photoconductive plate 22 by the pick off means 65 and is fed into the developing means through the guide means 75.

The closure of the contact 142 also energizes the lamp 76 so that the latent electrostatic image remaining on the photoconductive layer 24 is discharged after the electrostatic latent image on the photoconductive layer 24 has been transferred to the copy sheet 79. During the motion of the photoconductive plate 22 to the right, the edge 97 of said plate 22 pushes the rollers 95 down so that the levers 90 are pivoted in a clockwise direction (FIG. 4) about the shaft 86 to hold the friction wheels 85 out of engagement with the sheet 79 in the stack. Since the copy sheet 79 (FIG. 5) is nipped between the photoconductive plate 22 and the conductive roller 60, the copy sheet 79 is fed during the progress of the photoconductive plate 22 without being fed by the friction wheels 85. The friction wheels 85 are out of engagement with the stack of the copy sheets. Therefore a second copy sheet is not fed from the stack of the copy sheets, and only a single copy sheet is fed fromthe stack 83 during each copying cycle of the apparatus.

Since the motor 25 rotates faster in a clockwise direction than in a counterclockwise direction, the mounting table 12 and the photoconductive plate 22 make a quick return motion in the right direction. The connecting member 21 arrives at a travel limiting switch 150 which is located near the illumination slit 44. When the switch 150 is opened, the winding 134 of the relay 135 is deenergized so that the contacts 136, 141 and. 142 of the relay 135 are opened. The opening of the contact 141 causes the reversible motor 25 to stop so that the chain 30 is no longer driven and the mounting table 12 and the photoconductive plate 22 terminate their movement and occupy the original position as shown in FIG. 1. The sheet separated from the photoconductive plate 22 is fed into the developing vessel 100 so that the electroscopic powder from the liquid developer is selectively deposited on the surface of the copy sheet to convert the latent electrostatic image into a visible image. The copy sheet is further fed into the passage way defined by the guide member 114 and is dried by the warm air. After the drying of the copy sheet by the drying means, the dried copy sheet is discharged from the outlet opening 115 of the housing 11.

It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing its material advantages, the form hereinbefore described and illustrated in the drawings being merely a preferred embodiment thereof.

What is claimed is:

l. A copying apparatus for producing a visible image of an original on a copy sheet which has a conductive base and a dielectric surface, said apparatus comprismg:

a. a housing;

b. first means structurally associated with said housing and including a mounting table which has a flat mounting surface for supporting the original in a fiat condition and a photoconductive plate which has a conductive backing plate and a photoconductive surface, and which is secured to said mounting table with said photoconductive surface parallel with said mounting surface;

c. charging means in said housing adjacent said photoconductive plate, said photoconductive plate and said charging means being movable relative to each other, said charging means imposing a uniform electrostatic charge on said photoconductive surface during the relative movement of said photoconductive plate, and said charging means;

d. an optical assembly between said mounting table and said photoconductive plate for forming an electrostatic latent image of said original on said photoconductive surface after said photoconductive surface is electrostatically charged, said optical assembly being composed of illumination means for illuminating said original on said mounting surface, a lens unit and mirrors for focusing a mirror image of the illuminated original upon said photoconductive surface, an illuminated original upon said photoconductive surface, and an elongated slit defining a path of reflected light from the mounting table to the lens unit and from the lens unit to the photoconductive surface for projection of a partial image of said original onto said photoconductive surface, one of said first means and said optical as sembly being movable relative to the other in a direction parallel with the mounting surface;

e. drive means coupled to the movable one of said first means and said optical assembly for moving said movable one in a first direction, and sequentially in a second direction opposite to said first direction so that said optical assembly scans said original and continuously projects a partial image of said original onto said photoconductive surface during said relative movement in the first direction;

f. control means coupled to said drive means for controlling said drive means;

g. sheet feed means adjacent said photoconductive plate copy sheets one by one from a source of copy sheets with the dielectric surface of each copy sheet facing said photoconductive surface having the electrostatic latent image formed thereon;

h. charge transfer means adjacent said photoconductive plate for transferring said latent image from said photoconductive surface to said dielectric surface and including means for pressing said dielectric surface against said photoconductive surface and means for separating said copy sheet from said photoconductive plate;

guide means adjacent said charge transfer means for receiving and guiding said copy sheet in a predetermined path after said copy sheet is separated from said photoconductive surface; and j. developing means adjacent said guide means for converting said electrostatic latent image on said dielectric surface to a visible image.

2. The copying apparatus as claimed in claim 1 wherein said optical assembly is fixed to said housing and said first means is driven by said drive means in a direction parallel with the mounting surface.

3. The copying apparatus as claimed in claim v1 wherein said optical assembly comprises illumination means for illuminating the original, and arranged along an optical axis a first mirror inclined at a 45 angle relative to said mounting surface, a second mirror inclined at a 90 angle relative to said first mirror, a lens unit between said first mirror and said second mirror and which has an optical axis parallel with the first direction of the relative movement.

4. The copying apparatus as claimed in claim 1 wherein said control means is further coupled to and controls said charging means, said illumination means and said charge transfer means, whereby said charging means imposes a uniform electrostatic charge on said photoconductive surface and the illumination means illuminates said original during the relative movement of said first means to said optical assembly in the first direction, and said charge transfer means acts to transfer the electrostatic latent image on said photoconductive surface to said dielectric surface of said copy sheet during said relative movement in the second direction.

5. The copying apparatus as claimed in claim 4 further comprising discharging means adjacent said photoconductive surface for discharging an electrostatic latent image remaining on said photoconductive surface by illuminating said photoconductive surface during the relative movement of said first means to said optical assembly in the second direction after the electrostatic latent image on the photoconductive surface is transferred to the surface of the copy sheet.

6. The copying apparatus as claimed in claim 4 wherein said sheet feed means engages said photoconductive plate and said plate includes means to engage the sheet feed means to actuate the sheet feed means to initiate the sheet feeding operation at a predetermined position of said photoconductive plate.

7. A copying apparatus for producing a visible image of an original on a copy sheet which has a conductive base and a dielectric surface, said apparatus comprising:

a. a housing;

b. a photoconductive plate in said housing and having a conductive backing plate and a photoconductive surface;

c. support means on said housing for supporting said original;

d. charging means in said housing adjacent said photoconductive plate, said photoconductive plate and said charging means being movable relative to each other, said charging means imposing a uniform electrostatic charge on said photoconductive surface during the relative movement of said photoconductive plate and said charging means;

e. an optical assembly between said support means and said photoconductive plate for forming an electrostatic latent image of said original on said photoconductive surface after said photoconductive surface is electrostatically charged, said optical assembly including illumination means for illuminatingsaid original on said support means and a lens unit for projecting the light image of said original onto said photoconductive surface;

f. sheet, feed means adjacent said photoconductive plate for feeding to said photoconductive plate copy sheets one by one from a source of copy sheets with the dielectric surface of each copy sheet facing said photoconductive surface having the electrostatic latent image formed thereon;

g. charge transfer means adjacent said photoconductive plate for transferring said latent image from said photoconductive surface to said dielectric surface and including an electrically conductive rubber roller which is electrically coupled to the conductive backing plate of said photoconductive plate, means urging said roller toward said photoconductive plate for pressing the dielectric surface of said copy sheet against said photoconductive surface of said photoconductive plate and means for separating'the copy sheet from the photoconductive surface of said photoconductive plate after the copy sheet is pressed against the photoconductive surface by said conductive roller, whereby said conductive base of said copy sheet is electrically connected to said conductive backing plate of said photoconductive plate through said conductive roller at the time when the dielectric surface of said copy sheet is pressed against the photoconductive surface of said photoconductive plate and is separated from said photoconductive surface;

h. guide means adjacent said charge transfer means for receiving and guiding said copy sheet in a predetermined path after said copy sheet is separated from said photoconductive surface; and

i. developing means adjacent said guide means for converting said electrostatic latent image on said dielectric surface to a visible image.

8. A copying apparatus for producing a visible image of an original on a copy sheet which has a conductive base and a dielectric surface, said apparatus comprismg:

a. a housing;

b. a plane flat photoconductive plate in said housing and having a conductive backing plate and a photoconductive surface;

c. support means on said housing for supporting said original;

d. charging means in said housing adjacent said photoconductive plate;

e. an optical assembly between said support means and said photoconductive plate for forming an electrostatic latent image of said original on said photoconductive surface after said photoconductive surface is electrostatically charged, said optical assembly including illumination means for illuminating said original on said support means and a lens unit for projecting the light image of said original onto said photoconductive surface;

f. sheet feed means a adjacent said photoconductive plate for feeding to said photoconductive plate copy sheets one by one from a source of copy sheets with the dielectric surface of each copy sheet facing said photoconductive surface having the electrostatic latent image formed thereon;

g. charge transfer means adjacent said photoconductive plate for transferring said latent image from said photoconductive surface to said dielectric surface and including an electrically conductive roller which is electrically coupled to the conductive backing plate of said photoconductive plate, means I urging said roller toward said photoconductive plate for pressing the dielectric surface of said copy sheet against said photoconductive surface of said photoconductive plate and means for separating the copy sheet from the photoconductive surface of said photoconductive plate after the copy sheet is pressed against the photoconductive surface by said conductive roller, whereby said conductive base of said copy sheet is electrically connected to said conductive backing plate of said photoconductive plate through said conductive roller at the time when the dielectric surface of said copy sheet is pressed against the photoconductive surface of said photoconductive plate and is separated from said photoconductive surface, said photoconductive' plate being movable relative to said charging means, said optical assembly and said charge transfer means, whereby said charging means imposes said uniform electrostatic charge on said photoconductive surface and said optical assembly projects said light image of said original toward said photoconductive surface during the relative movement of said photoconductive plate to said charging means, optical assembly and said charge transfer means in a first direction, and said charge transfer means acts to transfer the electrostatic latent image on said photoconductive surface to said dielectric surface of said copy sheet during the relative movement in a second direction;

h. guide means adjacent said charge transfer means for receiving and guiding said copy sheet in a predetermined path after said copy sheet is separated from said photoconductive surface; and

i. developing means adjacent said guide means for converting said electrostatic latent image on said dielectric surface to a visible image.

9. An electrophotographic copying machine of the transfer type, comprising:

a carriage mounted to reciprocate along the top surface of the housing of said copying machine and including a transparent plate for supporting an original thereon;

an exposure device including an exposure window and an optical system for projecting a mirror image of said original placed on said transparent plate to said exposure window;

a conveying path along the imaging plane of said optical system and in parallel with said carriage;

a flexible sheet-like photosensitive member movable along said conveying path;

a charging device facing said photosensitive member. a transfer roller for contacting said photosensitive member, said charging device and said roller mounted along said conveying path so as to be located on opposite sides of said exposure window;

material towards a development device. 

1. A copying apparatus for producing a visible image of an original on a copy sheet which has a conductive base and a dielectric surface, said apparatus comprising: a. a housing; b. first means structurally associated with said housing and including a mounting table which has a flat mounting surface for supporting the original in a flat conditioN and a photoconductive plate which has a conductive backing plate and a photoconductive surface, and which is secured to said mounting table with said photoconductive surface parallel with said mounting surface; c. charging means in said housing adjacent said photoconductive plate, said photoconductive plate and said charging means being movable relative to each other, said charging means imposing a uniform electrostatic charge on said photoconductive surface during the relative movement of said photoconductive plate, and said charging means; d. an optical assembly between said mounting table and said photoconductive plate for forming an electrostatic latent image of said original on said photoconductive surface after said photoconductive surface is electrostatically charged, said optical assembly being composed of illumination means for illuminating said original on said mounting surface, a lens unit and mirrors for focusing a mirror image of the illuminated original upon said photoconductive surface, an illuminated original upon said photoconductive surface, and an elongated slit defining a path of reflected light from the mounting table to the lens unit and from the lens unit to the photoconductive surface for projection of a partial image of said original onto said photoconductive surface, one of said first means and said optical assembly being movable relative to the other in a direction parallel with the mounting surface; e. drive means coupled to the movable one of said first means and said optical assembly for moving said movable one in a first direction, and sequentially in a second direction opposite to said first direction so that said optical assembly scans said original and continuously projects a partial image of said original onto said photoconductive surface during said relative movement in the first direction; f. control means coupled to said drive means for controlling said drive means; g. sheet feed means adjacent said photoconductive plate copy sheets one by one from a source of copy sheets with the dielectric surface of each copy sheet facing said photoconductive surface having the electrostatic latent image formed thereon; h. charge transfer means adjacent said photoconductive plate for transferring said latent image from said photoconductive surface to said dielectric surface and including means for pressing said dielectric surface against said photoconductive surface and means for separating said copy sheet from said photoconductive plate; i. guide means adjacent said charge transfer means for receiving and guiding said copy sheet in a predetermined path after said copy sheet is separated from said photoconductive surface; and j. developing means adjacent said guide means for converting said electrostatic latent image on said dielectric surface to a visible image.
 2. The copying apparatus as claimed in claim 1 wherein said optical assembly is fixed to said housing and said first means is driven by said drive means in a direction parallel with the mounting surface.
 3. The copying apparatus as claimed in claim 1 wherein said optical assembly comprises illumination means for illuminating the original, and arranged along an optical axis a first mirror inclined at a 45* angle relative to said mounting surface, a second mirror inclined at a 90* angle relative to said first mirror, a lens unit between said first mirror and said second mirror and which has an optical axis parallel with the first direction of the relative movement.
 4. The copying apparatus as claimed in claim 1 wherein said control means is further coupled to and controls said charging means, said illumination means and said charge transfer means, whereby said charging means imposes a uniform electrostatic charge on said photoconductive surface and the illumination means illuminates said original during the relative movement of said first means to said optical assembly in the first direction, and said charge transfer means acts to transfer the electrostatic latent image on said photoconductive surface to said dielectric surface of said copy sheet during said relative movement in the second direction.
 5. The copying apparatus as claimed in claim 4 further comprising discharging means adjacent said photoconductive surface for discharging an electrostatic latent image remaining on said photoconductive surface by illuminating said photoconductive surface during the relative movement of said first means to said optical assembly in the second direction after the electrostatic latent image on the photoconductive surface is transferred to the surface of the copy sheet.
 6. The copying apparatus as claimed in claim 4 wherein said sheet feed means engages said photoconductive plate and said plate includes means to engage the sheet feed means to actuate the sheet feed means to initiate the sheet feeding operation at a predetermined position of said photoconductive plate.
 7. A copying apparatus for producing a visible image of an original on a copy sheet which has a conductive base and a dielectric surface, said apparatus comprising: a. a housing; b. a photoconductive plate in said housing and having a conductive backing plate and a photoconductive surface; c. support means on said housing for supporting said original; d. charging means in said housing adjacent said photoconductive plate, said photoconductive plate and said charging means being movable relative to each other, said charging means imposing a uniform electrostatic charge on said photoconductive surface during the relative movement of said photoconductive plate and said charging means; e. an optical assembly between said support means and said photoconductive plate for forming an electrostatic latent image of said original on said photoconductive surface after said photoconductive surface is electrostatically charged, said optical assembly including illumination means for illuminating said original on said support means and a lens unit for projecting the light image of said original onto said photoconductive surface; f. sheet feed means adjacent said photoconductive plate for feeding to said photoconductive plate copy sheets one by one from a source of copy sheets with the dielectric surface of each copy sheet facing said photoconductive surface having the electrostatic latent image formed thereon; g. charge transfer means adjacent said photoconductive plate for transferring said latent image from said photoconductive surface to said dielectric surface and including an electrically conductive rubber roller which is electrically coupled to the conductive backing plate of said photoconductive plate, means urging said roller toward said photoconductive plate for pressing the dielectric surface of said copy sheet against said photoconductive surface of said photoconductive plate and means for separating the copy sheet from the photoconductive surface of said photoconductive plate after the copy sheet is pressed against the photoconductive surface by said conductive roller, whereby said conductive base of said copy sheet is electrically connected to said conductive backing plate of said photoconductive plate through said conductive roller at the time when the dielectric surface of said copy sheet is pressed against the photoconductive surface of said photoconductive plate and is separated from said photoconductive surface; h. guide means adjacent said charge transfer means for receiving and guiding said copy sheet in a predetermined path after said copy sheet is separated from said photoconductive surface; and i. developing means adjacent said guide means for converting said electrostatic latent image on said dielectric surface to a visible image.
 8. A copying apparatus for producing a visible image of an original on a copy sheet which has a conductive base and a dielectric surface, said apparatus comprising: a. a housing; b. a plane flat photoconductive plate in said housinG and having a conductive backing plate and a photoconductive surface; c. support means on said housing for supporting said original; d. charging means in said housing adjacent said photoconductive plate; e. an optical assembly between said support means and said photoconductive plate for forming an electrostatic latent image of said original on said photoconductive surface after said photoconductive surface is electrostatically charged, said optical assembly including illumination means for illuminating said original on said support means and a lens unit for projecting the light image of said original onto said photoconductive surface; f. sheet feed means a adjacent said photoconductive plate for feeding to said photoconductive plate copy sheets one by one from a source of copy sheets with the dielectric surface of each copy sheet facing said photoconductive surface having the electrostatic latent image formed thereon; g. charge transfer means adjacent said photoconductive plate for transferring said latent image from said photoconductive surface to said dielectric surface and including an electrically conductive roller which is electrically coupled to the conductive backing plate of said photoconductive plate, means urging said roller toward said photoconductive plate for pressing the dielectric surface of said copy sheet against said photoconductive surface of said photoconductive plate and means for separating the copy sheet from the photoconductive surface of said photoconductive plate after the copy sheet is pressed against the photoconductive surface by said conductive roller, whereby said conductive base of said copy sheet is electrically connected to said conductive backing plate of said photoconductive plate through said conductive roller at the time when the dielectric surface of said copy sheet is pressed against the photoconductive surface of said photoconductive plate and is separated from said photoconductive surface, said photoconductive plate being movable relative to said charging means, said optical assembly and said charge transfer means, whereby said charging means imposes said uniform electrostatic charge on said photoconductive surface and said optical assembly projects said light image of said original toward said photoconductive surface during the relative movement of said photoconductive plate to said charging means, optical assembly and said charge transfer means in a first direction, and said charge transfer means acts to transfer the electrostatic latent image on said photoconductive surface to said dielectric surface of said copy sheet during the relative movement in a second direction; h. guide means adjacent said charge transfer means for receiving and guiding said copy sheet in a predetermined path after said copy sheet is separated from said photoconductive surface; and i. developing means adjacent said guide means for converting said electrostatic latent image on said dielectric surface to a visible image.
 9. An electrophotographic copying machine of the transfer type, comprising: a carriage mounted to reciprocate along the top surface of the housing of said copying machine and including a transparent plate for supporting an original thereon; an exposure device including an exposure window and an optical system for projecting a mirror image of said original placed on said transparent plate to said exposure window; a conveying path along the imaging plane of said optical system and in parallel with said carriage; a flexible sheet-like photosensitive member movable along said conveying path; a charging device facing said photosensitive member, a transfer roller for contacting said photosensitive member, said charging device and said roller mounted along said conveying path so as to be located on opposite sides of said exposure window; means for supplying sheet-like transfer material for receiving the image on said photosensitive member; means for separating said Sheet-like material from said photosensitive member; a driving member for moving said photosensitive member to confront said charging device, said exposure window, said transfer roller and said means for separating, and also to another position where it is separated therefrom; a guide member and a supplying member for feeding said transfer material from said means for supplying onto said photosensitive member; and a member for transporting said separated transfer material towards a development device. 